US5124628A - Gate pulse generator of a reactive power compensation device - Google Patents

Gate pulse generator of a reactive power compensation device Download PDF

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Publication number
US5124628A
US5124628A US07/683,811 US68381191A US5124628A US 5124628 A US5124628 A US 5124628A US 68381191 A US68381191 A US 68381191A US 5124628 A US5124628 A US 5124628A
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United States
Prior art keywords
thyristor
gate pulse
signal
gate
thyristors
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Expired - Fee Related
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US07/683,811
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English (en)
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Hideshi Ogiwara
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Toshiba Corp
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Toshiba Corp
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
    • H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
    • H02J3/1864—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein the stepless control of reactive power is obtained by at least one reactive element connected in series with a semiconductor switch
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/08—Modifications for protecting switching circuit against overcurrent or overvoltage
    • H03K17/081—Modifications for protecting switching circuit against overcurrent or overvoltage without feedback from the output circuit to the control circuit
    • H03K17/0812—Modifications for protecting switching circuit against overcurrent or overvoltage without feedback from the output circuit to the control circuit by measures taken in the control circuit
    • H03K17/08124—Modifications for protecting switching circuit against overcurrent or overvoltage without feedback from the output circuit to the control circuit by measures taken in the control circuit in thyristor switches
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
    • H03K17/72—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices having more than two PN junctions; having more than three electrodes; having more than one electrode connected to the same conductivity region
    • H03K17/725—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices having more than two PN junctions; having more than three electrodes; having more than one electrode connected to the same conductivity region for ac voltages or currents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/10—Flexible AC transmission systems [FACTS]

Definitions

  • the present invention relates to a reactive power compensation device, and more particularly to a thyristor switch gate pulse generator for capacitor load switching in a reactive power compensation device.
  • TCRs thyristor controlled reactors
  • TSCs thyristor switched capacitors
  • TCRs constituted by series connections of large numbers of thyristors. Since the load of a TSC is a capacitor, it functions as an on-off switch and a gate pulse generator that switches the thyristors on and off must be able to switch a large number of thyristors on and off all together at high speed.
  • FIG. 3 is a block diagram of a typical TSC.
  • a capacitor 2, a reactor 4 and a thyristor converter 8 constituted by a gate pulse generator 6 which produces gate pulse signals for thyristors 3U and 3X in response to on-off commands from a control unit 7 are connected in series to a TSC transformer 1.
  • Reference numeral 5 designates a circuit for detection of thyristor switch 3U and 3X voltage.
  • FIG. 4 shows the waveforms during normal operation of the various sections of the TSC shown in FIG. 3.
  • VS is the primary voltage of the TSC transformer and
  • IC and VC are the current and voltage of the capacitor constituting the load of the thyristor converter.
  • PHS indicates phase control signals (referred to below as PHS) which are output by control unit 7 and are produced at the peak phase of power supply voltage VS to make the TSC converter excitation rush current minimum.
  • a narrow gate pulse system is one in which triggering signals in the form of one-shot pulses are supplied to thyristors at thyristor triggering times and compared to a conventional broad pulse system. It has the advantage that it is possible to make the power supply circuit of the gate pulse generator smaller and cheaper, etc.
  • FIG. 5 shows a gate pulse generator in a narrow gate pulse system.
  • Reference numerals 8U and 8X designate flip-flop circuits, 9U and 9X AND gates, 10U and 10X one-shot circuits that output set pulse widths, 11U and 11X OR gates, 12 a one-shot circuit, 13 an AND gate, 14 a time delay circuit that outputs a signal after a set delay, 15 an AND gate and 16 a time delay circuit.
  • Flip-flop circuit 8U is set by a PHS(U) pulse output by the control circuit 7.
  • a gate pulse signal GP(U) (referred to as GP below) of set width is output by one-shot circuit 10U and supplied to a gate of a thyristor switch only when the logical product of the forward voltage signal FV(U) of thyristor 3U and the Q output of flip flop 8U at AND gate 9U is "1".
  • Flip-flop circuit 8U that has been set by a PHS(U) pulse is reset by the logical sum output of OR gate 11U.
  • time delay circuit 14 becomes "1" only if a state in which both the forward voltage signal FV(U) and the reverse voltage signal FV(X) are not present in a set time after supply of a gate pulse signal GP(X) to opposite-phase thyristor switch 3X has continued for more than the thyristor turn-off time.
  • Output signals of time delay circuit 16 are supplied to the other input of OR gate 11U.
  • time delay circuit 16 becomes "1" when a reverse voltage is imposed for more than the turn-off time after stopping.
  • Gate pulses GP(U) are output while setting of flip-flop circuit 8U by PHS(U) pulses and resetting of 8U by the two types of signals described above are alternately repeated.
  • FIG. 6A is a waveform timing diagram showing waveforms during the TSC operation, and particularly illustrates the TSC converter 1 secondary side voltage VS, capacitor current and voltage IC and VC, the voltage V A-K across opposite electrodes of thyristor switch 3U and the forward side and reverse side gate pulse signals GP(U) and GP(X).
  • the waveforms of FIG. 6A are representative of normal operation of the circuit shown in FIG. 5.
  • FIG. 6B illustrates operation of the circuit shown in FIG. 5 in the case where an intermittence of current occurs.
  • the particular waveforms shown in FIG. 6B illustrate the case where the capacitor current IC is made intermittent by a system voltage surge.
  • the AND condition of 9U (or 9X) is established and GPs of both phases are output out of synchronism with the PHS signals and protection against partial commutation failure of thyristor switches 3U and 3X is effected. If, subsequently, the intermittency of the current comes to an end and there is a move to normal conduction, the conditions for the resetting circuits of flip-flops 8U and 8X are established and so the flip-flops of both phases are reset.
  • Action by the resetting circuit of flip-flop 8U is a correct action but since flip-flop 8X is reset soon after own-phase conduction starts, GP output becomes impossible even if the current is intermittent when X phase conduction ends and therefore partial commutation failure is caused and one can anticipate breakdown of thyristor elements.
  • FIG. 6B Next described in more detail in relation to the waveform shown in FIG. 6B is a mechanism by which partial commutation failure occurs.
  • two intermittences occur at t2 and t7.
  • Flip-flop 8X is reset at time t5, which is delayed from t2 by the delay time Td.
  • the prior art circuit shown in FIG. 5 has the problem that if a second intermittence occurs at t7 and terminates at t8, GP(X) cannot be generated.
  • GP(X) can be generated when the state of F.F.(U) is "1". As the state of F.F.(U) is "0" at t8 (see FIG. 6B), GP(X) cannot be generated at t8.
  • the thyristor 3X is turned off at t7 because the reverse voltage is applied to the thyristor 3X.
  • the forward voltage is applied to the thyristor 3X at t8, and some elements of the thyristor 3X may turn on and other elements may not turn on.
  • a partial commutation failure may occur due to differences in the characteristics of the thyristor elements when the forward voltage is applied to the thyristor before the turn-off time. Partial commutation failure occurs in the absence of GP(X) due to the characteristics of thyristors connected in series. In series connection, there is a dispersion in turn-off time of the series connected thyristors. Each thyristor has its own turn-off time.
  • a positive voltage is applied to a thyristor in a short time after turn-off, the thyristor turns on in the absence of a gate pulse. If the positive voltage is applied at the point after "turn-off time", the thyristors do not turn on in the absence of a gate pulse.
  • Tmin refers to the minimum turn-off time of the thyristors and Tmax refers to the maximum turn-off time of the thyristors.
  • Tmax refers to the maximum turn-off time of the thyristors.
  • some elements are turned on and the other elements are maintained in the off condition, which results in a partial commutation failure condition. If a small number of thyristors, such as, only one thyristor is in the off condition, the total voltage is then applied to that one thyristor thereby destroying that thyristor.
  • the delay time Td of the delay timer 14 is set so that Td is greater than the turn-off time of the thyristor.
  • F.F.(U) is reset at t6 by GP(U) after a time delay Td after t2.
  • one object of this invention is to provide a novel gate generator for a reactive power compensation device which during TSC operation confirms that a satisfactory turn-off time has been ensured and makes it possible to reset only the flip-flop circuits of phases which it is all right to reset and which, by outputting GPs prior to this, forcibly retriggers thyristor elements and so prevents partial commutation failure and breakdown of the thyristor elements.
  • Another object of this invention is to provide a new and improved gate pulse generator as above described, which distinguishes between correctly timed gate pulses and phase voltages (versus intermittences) and gate pulses that are out of synchronism, and which avoids resetting the GP flip-flop of FIG. 5 if the gate pulses are not correctly timed.
  • a new and improved gate pulse generator in a reactive power compensation device in which a capacitor is connected in series with thyristors that are connected in antiparallel and which is so devised that triggering pulses are produced and current is passed into the capacitor when both a signal of forward voltage imposed on the thyristors and a thyristor conduction period signal that is reset by a phase control signal are present, including means for resetting conduction period signals during conduction if both an inverted pair phase phase-control signal and a triggering pulse are present after a set time.
  • the gate pulse generator of the present invention includes a circuit which, on condition that there is present an own-phase gate pulse that has been emitted within a set time after input of a voltage (PHS) signal from a control unit, resets the flip-flop of the opposite phase. Due to the addition of this circuit, upon the following output of an opposite-phase gate pulse (GP), even if the conventional resetting condition occurs wherein there is an absence both of a GV(U) signal and of an FV(X) signal for more than a set time, flip-flop resetting is effected only if the opposite-phase GP is correctly timed.
  • PHS voltage
  • FIG. 1 is a block diagram of one embodiment of the gate pulse generation circuit of the present invention
  • FIGS. 2A, 2B and 2C are waveform diagrams illustrating waveforms produced at various sections of a TSC by a gate pulse generation circuit of the present invention under various operating conditions;
  • FIG. 3 is a circuit diagram of a typical TSC
  • FIG. 4 is a waveform diagram of waveforms at different sections, of the TSC for giving an understanding the operation of the TSC;
  • FIG. 5 is a block diagram of a conventional narrow gate pulse type gate pulse generation circuit
  • FIGS. 6A and 6B are waveform diagrams illustrating waveforms at various sections during various conditions of operation of the TSC driven by gate pulses produced by the circuit of FIG. 5.
  • the gate pulse generator of the present invention includes essentially identical circuits for generating the U-phase gate pulses GP(U) and X-phase gate pulses GP(X).
  • signals PHS(U), FV(U), PHS(X), FV(X), and GB are applied to the gate pulse generator circuit.
  • signals PHS(U) and PHS(X) are produced by control circuit 7 at the maximum forward and reverse voltages of VS, respectively.
  • the signal FV(X) is at a logic level "1" when the signal V A-K shown in FIGS. 2A-2C and 6A-6B is negative and a logic level "0" when the signal V A-K is positive.
  • Signal FV(U) is positive when the signal V A-K is positive, and vice versa.
  • the signal V A-K is the voltage across the anode and cathode of the thyristor 3U shown in FIG. 3.
  • the signal F.F.(U) is the Q output of the flip-flop 8U
  • the signal F.F.(X) is the Q output of the flip-flop 8X.
  • the signal GB is a system stop signal.
  • reference numeral designations 8U and 8X designate flip-flops, 9U, 9X designate AND gates, 10U, 10X designate one-shot circuits, 11U, 11X designate OR gates, 12U, 12X designate one-shot circuits, 13U, 13X designate AND gates, 14U, 14X designate time delay circuits, 15U, 15X designate AND gates, 16U, 16X designate time delay circuits, 17U, 17X designate one-shot circuits, and 18U, 18X designate AND gates.
  • FIG. 1 reference numeral designations 8U and 8X designate flip-flops, 9U, 9X designate AND gates, 10U, 10X designate one-shot circuits, 11U, 11X designate OR gates, 12U, 12X designate one-shot circuits, 13U, 13X designate AND gates, 14U, 14X designate time delay circuits, 15U, 15X designate AND gates, 16U, 16X designate time delay circuits, 17U, 17X designate one-shot circuit
  • the gate pulse generator of the present invention further includes the provision of one-shot circuit 17U and AND gate 18U for controlling generation of the reset pulse fed back to the flip-flop circuit 8X, and corresponding circuits 17X and 18X for controlling generation of a resetting pulse applied to the flip-flop 8U.
  • a PHS(X) signal causes the one-shot circuit 17X to output a one-shot pulse of set width and the logical product of this pulse and GP(X) is taken at the output of AND gate 18X.
  • the output signal of AND gate 18X is applied to one-shot circuit 12X which produces a pulse applied to the AND gate 13U, which, if FV(U) and FV(X) are "0", after a time delay produced by time delay circuit 14U is applied via OR gate 11U to the reset terminal of flip-flop 8U.
  • This chain of circuit elements forms a U phase flip-flop resetting circuit, whereas corresponding circuits for the X phase flip-flop 8X, above-identified, comprise an X phase flip-flop resetting circuit.
  • gate pulses that are out of synchronism with the PHS(U) and PHS(X) signals can be output, and partial commutation failure and breakdown of thyristor elements can be prevented.
  • FIG. 2A shows a normal operation of the circuit shown in FIG. 1.
  • FIG. 2B shows the case where a current intermittence occurs.
  • FIG. 2C is an enlarged view of a portion of FIG. 2B where a current intermittence occurs.
  • GP(X) can be generated at t8 because F.F.(U) has not yet reset at t8.
  • gate pulses that are out of synchronism with the PHS signals can be output and partial commutation failure and breakdown of thyristor elements can be prevented.
  • the present invention causes no drawbacks, since the additional circuits which prevent partial commutation failure do not disturb the conventional reset circuits and functions typically performed.
  • own-phase flip-flop resetting is effected if a correctly timed opposite-phase gate pulse is output.
  • flip-flop resetting is effected only if gate pulses are correctly timed and even if the current is subsequently intermittent, it is possible to output gate pulses that are out of synchronism with the PHS signals.
  • the present invention therefore makes it possible to provide a highly reliable static type reactive power compensation device in which thyristor elements are protected from partial commutation failure and breakdown.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Electrical Variables (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
  • Power Conversion In General (AREA)
US07/683,811 1990-04-12 1991-04-11 Gate pulse generator of a reactive power compensation device Expired - Fee Related US5124628A (en)

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JP2-95153 1990-04-12
JP2095153A JP2786717B2 (ja) 1990-04-12 1990-04-12 無効電力補償装置のゲートパルス発生装置

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US (1) US5124628A (de)
EP (1) EP0452049B1 (de)
JP (1) JP2786717B2 (de)
AU (1) AU637682B2 (de)
CA (1) CA2040211C (de)
DE (1) DE69121448T2 (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5969509A (en) * 1997-02-06 1999-10-19 Asea Brown Boveri Ab Method and a device for control of a capacitor device for a shunt-connected compensator unit
US6121758A (en) * 1999-06-23 2000-09-19 Daq Electronics, Inc. Adaptive synchronous capacitor switch controller
CN107681678A (zh) * 2017-08-31 2018-02-09 国网河南省电力公司电力科学研究院 一种基于整流侧触发角紧急控制的换相失败预防方法
CN109525001A (zh) * 2018-11-16 2019-03-26 国网河南省电力公司电力科学研究院 特高压分层接入下的换相失败预防协调控制方法及系统

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69841351D1 (de) * 1997-02-06 2010-01-21 Abb Ab Verfahren und Vorrichtung zur Steuerung einer kapazitiven Vorrichtung für eine Nebenschluss-Kompensatoreinheit
CN105717846B (zh) * 2016-04-13 2018-08-17 上海电器科学研究院 电子式智能精准角度选择控制装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4633381A (en) * 1985-02-26 1986-12-30 Sundstrand Corporation Inverter shoot-through protection circuit
US4641231A (en) * 1985-12-06 1987-02-03 General Electric Company Apparatus and method for failure testing of a control turn-off semiconductor
US4829415A (en) * 1987-03-17 1989-05-09 Rca Licensing Corporation Push-pull drive circuit for a power converter
US4859884A (en) * 1987-07-10 1989-08-22 Kabushiki Kaisha Toshiba Gate signal generator for thyristor valve

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59110335A (ja) * 1982-12-14 1984-06-26 富士電機株式会社 サイリスタ式コンデンサ開閉装置
JPH02272612A (ja) * 1989-04-14 1990-11-07 Toshiba Corp 静止形無効電力補償装置のゲートパルス発生方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4633381A (en) * 1985-02-26 1986-12-30 Sundstrand Corporation Inverter shoot-through protection circuit
US4641231A (en) * 1985-12-06 1987-02-03 General Electric Company Apparatus and method for failure testing of a control turn-off semiconductor
US4829415A (en) * 1987-03-17 1989-05-09 Rca Licensing Corporation Push-pull drive circuit for a power converter
US4859884A (en) * 1987-07-10 1989-08-22 Kabushiki Kaisha Toshiba Gate signal generator for thyristor valve

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
IEE pp. 183 188 Thyristor Switched Capacitor, TSC, in Theory and Practice 1 1985, ASEA AB, Sweden. *
IEE-pp. 183-188 "Thyristor Switched Capacitor, TSC, in Theory and Practice"1 1985, ASEA AB, Sweden.

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5969509A (en) * 1997-02-06 1999-10-19 Asea Brown Boveri Ab Method and a device for control of a capacitor device for a shunt-connected compensator unit
US6121758A (en) * 1999-06-23 2000-09-19 Daq Electronics, Inc. Adaptive synchronous capacitor switch controller
CN107681678A (zh) * 2017-08-31 2018-02-09 国网河南省电力公司电力科学研究院 一种基于整流侧触发角紧急控制的换相失败预防方法
CN107681678B (zh) * 2017-08-31 2020-05-29 国网河南省电力公司电力科学研究院 一种基于整流侧触发角紧急控制的换相失败预防方法
CN109525001A (zh) * 2018-11-16 2019-03-26 国网河南省电力公司电力科学研究院 特高压分层接入下的换相失败预防协调控制方法及系统

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Publication number Publication date
DE69121448D1 (de) 1996-09-26
CA2040211C (en) 1997-08-05
JP2786717B2 (ja) 1998-08-13
CA2040211A1 (en) 1991-10-13
EP0452049A2 (de) 1991-10-16
EP0452049A3 (en) 1992-03-04
JPH03294913A (ja) 1991-12-26
AU637682B2 (en) 1993-06-03
DE69121448T2 (de) 1997-01-16
EP0452049B1 (de) 1996-08-21
AU7432391A (en) 1991-10-17

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